The present invention relates to a thermal transfer recording medium, in particular, to a thermal transfer recording medium that excels in image definition, characterized in that its adhesion is enough even for a transferee medium of poor smoothness, and, therefore, deposition of printed characters is satisfactory. Even in a high speed printing operation, a heat softening layer is readily transferred from a support onto a transferee medium, thereby high print quality is achieved.
Recently, more common use of the thermal transfer recording apparatuses such as a wordprocessor is entailing more common use of the thermal transfer recording medium comprising a support having thereon a heat softening layer.
However, the conventional thermal transfer recording medium has fundamental problems such as print quality that is readily affected by the smoothness of a transferee medium (e.g. a transfer sheet); poor deposition of printed images; and, and when used at higher printing speed results in disproportionally poor print quality.
To overcome these problems, there have been various attempts for improving deposition of printed images; one attempt is a multilayer heat softening layer on a thermal transfer recording medium; and in another attempt, various additives are incorporated into a heat softening layer.
For example, a heat softening layer of one proposed thermal transfer recording medium comprises two layers, i.e. an intermediate layer and a heat-fusible ink layer, wherein the melting point of the intermediate layer that is adjacent to a support is lower than that of the heat-fusible ink layer disposed above the intermediate layer (Japanese Patent Publication Open to Public Inspection, hereinafter referred to as Japanese Patent O.P.I. Publication, No. 189492/1985).
According to this thermal transfer recording medium, the release of the ink layer from the support is enhanced by the presence of an intermediate layer, thereby the melting point of the heat-fusible ink layer can be higher than that of a thermal transfer recording medium lacking such an intermediate layer and deposition of the resultant printed image is positively improved.
This thermal transfer recording medium, however, provides yet insufficient adhesion relative to a transferee medium: smudge or streaking readily occurs when printing is performed with a transferee medium of poor surface smoothness, or when high speed printing is performed, resulting in degraded print quality.